Thread: Char Help! "Packing " bits to a signle unsigned char

Originally Posted by itCbitC

An unsigned char can only hold values from 0-255 and you're trying to fit 01234567 into it.

Thanks for the reply, I do understand that. Maybe this will further explain what i am trying to do:

purpose of my function: the function prompts the user for input, reads 7 unsigned values representing data bits, and "packs" these bits into a single unsigned char


What should returned: unsigned char that represents the 7 bits of data entered by the user. The MSB of the character is always 0. If the data entered by the user is d6 .. d0, the format of the byte returned is:
MSB LSB
0 d6 d5 d4 d3 d2 d2 d0

Does this make any sense?

One was using an array

Can be done.

Code:

const int MAXBITS = 7;

unsigned char ones_and_zeroes[MAXBITS  + 2] = "" ;  /*Holds 1'and zeroes*/
      /* one for '\0' and other for extra zero*/
     /*Now the input*/
     ....Make sure input has only 7 bits ,use fgets and don't forget to strip newline.
     /*After the input*/
     strrev(ones_and_zeroes);
     strcat(ones_and_zeroes, "0");
     strrev(ones_and_zeroes);

Your function returns an unsigned char

Code:

unsigned char getMessageByte()

But you are trying to return an unsigned char*. (ones_and_zeroes[] is an array)

So one way would be:

Code:

void getMessage(unsigned char* ones_and_zeroes) {
     . . .
     . . .
}
.
.
int main(void) {
   /* memory allocated in main*/ 
    unsigned char ones_and_zeroes[MAXBITS  + 2] = "" ;
    .
    .
    getMessage(ones_and_zeroes);/*Function call now with a parameter*/
    .
    .
    return 0;
}